In recent years, highly advanced illumination systems are being developed that allow consumers to obtain a desired ambiance for a particular room or space. These illumination systems move away from the traditional control of individual light sources (switching on/off and dimming) towards scene setting, where sets of light sources are controlled simultaneously. An example of such an illumination system is an arrangement of several sets of light sources in a room, a lobby, or a vehicle.
For these scene setting applications, intuitive user interaction is identified as one of the most important success factors. Providing a user with information related to the light sources, such as localized identification of the light sources, their capabilities, and there current settings, is key for enabling an intuitive interaction. One technique that has been proposed to provide the user with such information is based on embedding codes (also referred to as “identifiers”) identifying a light source or a group of light sources by modulating the light output of the illumination device in a manner so that the embedded codes are invisible to the consumers (such light output is sometimes referred to as “coded light” and abbreviated as “CL”). The embedded codes are detected by an optical receiver which may, for example, be implemented in a remote control for controlling the illumination devices or included in another unit such as a switch or a sensor device.
It has been previously shown how CL technology can be used for commissioning of lighting systems, e.g. by pointing to individual light sources and reading out their identifiers. Also, user interaction methods based on this technology have been developed, e.g. interactive scene setting using a photo sensor based receiver, and point-and-control based light source selection using a small array of photo detectors.
A drawback of the previous CL detection techniques is that only embedded codes present at single positions can be detected. In contrast, it is desired to characterize the whole two-dimensional (2D) scene in real time in terms of the identifiers being present, distinguishing the identifiers of the different light sources in a room/scene.
To eliminate this drawback, camera sensors have been proposed that can determine embedded codes present at multiple positions within an image. However, a drawback of the previous techniques employing camera sensors is that the acquisition time of the sensor must be equal to the duration of a single bit within the embedded code. Consecutive bits of the embedded code are then detected by analyzing results obtained in consecutive acquisitions of the camera. When CL is embedded in a manner that is invisible to a human eye (i.e., embedded at high frequency), such techniques require the use of advanced and, therefore, expensive cameras capable of providing high acquisition rate. Conventional low-cost camera sensors typically have too low of an acquisition rate to detect such high frequency CL. Therefore, currently, the only methods for CL detection that can work with conventional low-cost cameras require the identifiers to be embedded in such a manner that the CL modulation cannot be completely invisible because the viewers can visually perceive the low frequency modulation as flickering in the light.
As the foregoing illustrates, what is needed in the art is a technique for detecting CL embedded into a light output of light sources that addresses at least some of the problems described above.